ABC | Volume 110, Nº2, February 2018

Original Article Rodrigues et al Practices in Myocardial Perfusion Scintigraphy Arq Bras Cardiol. 2018; 110(2):175-180 Table 2 – Comparison of the mean numbers of myocardial perfusion scintigraphy (MPS) performed at the 63 nuclear medicine services N Mean Median Standard deviation p value Number of MPS per month ≥ 6 Good practices 13 298 280 230 0.043* < 6 Good practices 50 186 120 304 * Mann-Whitney U test Table 3 – Frequency (%) of the adoption of each good practice at the nuclear medicine services assessed in Brazil, 2016 Good practices Brazil A 63 (100) B 63 (100) C 27 (42.86) D 63 (100) E 4 (6.35) F 12 (19.05) G 33 (52.38) H 41 (65.08) A:Avoid thallium-stress protocol; B:Avoid dual-isotope protocol; C:Avoid high Tc-99m activities; D:Avoid high Tl-201 activities; E: Perform only “Stress-Only”; F: Use strategies focused on dose reduction; G: Patient’s weight-based activities; H:Avoid inappropriate activities that can generate the shine-through artifact. and reduced by 61% the use of radiopharmaceuticals and radiation exposure. Gowd et al. 14 have listed the limitations to its wide adoption, such as non-familiarity with the assessment of a single phase, the need for processing images immediately after their acquisition, and the issues regarding reimbursement of expenses, considering that a significant part of the test is paid with the resting phase. Oliveira et al. 15 have been the first to approach the use of that protocol in Brazil, but the experience is still incipient. An accurate test requires the use of proper radiation doses, avoiding the “shine-through” phenomenon. 16 One third of the NMS assessed still administer doses that can allow the interference of residual radiation with later images in the one-day protocol. 17 In that protocol, respecting the minimum three-hour interval between the phases, a dose three times higher than that of the first phase is required to avoid that artifact, which can lead to a reduction in the ischemic burden or even to false-negative results. 16 Recent studies have shown that protocols with ultra-low doses of sestamibi (5 mCi) during stress can be even more appropriate to prevent that artifact. 17 The IAEA has suggested the Tc-99m threshold of 36 mCi as the maximum activity to be administered in a single injection; 7 however, half of the NMS assessed use activities over that threshold. Such thresholds are usually exceeded when the patient has a high body weight, the best strategy for that patient being to undergo MPS in the two-day protocol, eliminating, thus, the need for tripling the dose, providing lower radiation exposure and higher image quality. 10 The adjustment of the dose for the patient’s weight is part of the CNEN norms and should be adopted as a rule. 18 Nevertheless, almost half of the NMS assessed have not adopted routinely this practice, missing an opportunity for improvement. That adjustment is aimed at using appropriate radiation doses to each patient’s weight and attenuation rate, preventing overexposure or insufficient exposure, which leads to a low quality test. 19 In addition, strategies for dose reduction have been considered. There is high-technology hardware, such as CZT cameras, 20,21 which provide high image resolution, and hybrid devices, such as SPECT-CT, which can eliminate the attenuation of soft tissues, 22 but they are not widely available. A strategy that can be used without additional costs for those without attenuation correction is the prone position during the acquisition of the stress phase of MPS. Placing the patient in the prone position reduces diaphragmatic attenuation and its interference with the images. 23,24 Many NMS have reported using that technique, but that can only be considered a strategy of dose reduction if the single stress phase is a practice adopted by the entire NMS. In proneMPS, the stress phase shows normal perfusion aspect and preserved contractility, but the patient should undergo the second phase anyhow. There was no dose reduction during that process. In general, the QI was significantly higher in the academic institutions. In 2010, the MPS performed inside university‑affiliated hospitals showed more appropriate and precise indications. 25 The NMS that promote research are constantly searching for knowledge, being updated by recent studies and new international recommendations very fast, being always one step ahead. Another important and innovative finding was the significantly higher QI of the institutions that count on a complete multiprofessional team, comprised by nuclear 178